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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Automatisk detektering av akustiska resonansfrekvenser i trästockar / Real time spectral analysis for acoustic resonance technique used in timber quality classification

Jonsson, David January 2012 (has links)
In order to measure the quality of the logs, one can with help of Fast Fourier Transform technique get the signals resonance peaks. With help of these peaks you can see whether the quality of a tree is good or bad. This report contains the work of a where a program has been developed to be able to process a vibration created by an automatic hammer hitting on a log of wood. From the processed signal the program should be able to show both the raw wavesignal and the processed measured data from the resonance peaks. Beyond the raw wavesignal and resonance peaks the program should also be able to control the automatic hammer. The goal with the project is to have a program that get the same measure results as an already functioning measuring equipment. The result was a success when with the help of the program you were both able to control the hammer, measure the results and save the data with an accurate results.
2

Timmerkvalitet hos björk i blandskog med gran / Timber quality of birch in mixed stands of birch and spruce

Andersson, Helena W., Rickardson, Anders January 2014 (has links)
Birch is the dominant deciduous tree species in Sweden but only 16 % is found in pure birch stands. The majority of the birch (51 %) is to be found in conifer dominated stands. Swedish forest land comprises approximately of 23 % mixed stands and one problem is that for mixed stands there are few management recommendations. The underlying aim of this thesis was to study the management of mixed forest stands of spruce and birch to achieve good timber quality of birch. The study was based on a literature study and measurement in a field experiment launched in 1998 by the Swedish University of Agricultural Sciences (SLU). This study indicates that it is possible to achieve good timber quality of birch in mixed stands of birch and spruce. However, it requires that birch in mixed stands with spruce should be managed similar to management programs of pure birch stands.   Keywords: Birch, spruce, timber quality, mixed stands.
3

Effects of Prescribed Fire on Timber Quality and Tree Value in the Central Hardwood Region

David Paul Mann (7471193) 17 October 2019 (has links)
<div>Prescribed fire is one of the most useful tools available to forest managers attempting to maintain oak-hickory forests in the Central Hardwood Region. Prescribed fire can be useful in promoting regeneration of desirable species groups like oak (Quercus spp.) and hickory (Carya spp.) by preparing the seedbed, managing competition, and creating canopy gaps. The use of prescribed fire has been limited by concerns regarding the effect of the practice on standing timber. A perception of strong negative effects to tree-quality and tree-value from fire originated largely from sometimes deleterious effects of wildfire on timber. Less research exists demonstrating the potential effects of controlled, prescribed burning on timber quality and value. Furthermore, most research that exists focuses on individual tree characteristics, and is often focused on a relatively small geographic areas.</div><div><br></div><div>I conducted a regional study on the effects of prescribed fire on timber quality across a gradient of the Central Hardwood Region, ranging from the Missouri Ozarks to the Appalachian foothills. I studied 139 stands in selected prescribed fire units and control sites in Mark Twain National Forest (MO), Hoosier National Forest (IN), Wayne National Forest (OH) and Daniel Boone National Forest (KY). Selected stands were dominated by hardwoods species and had variable prescribed fire histories, ranging from 0 to 6 prescribed fires. </div><div><br></div><div>Measurements were taken concurrently across this plot network for two studies. First, we assessed the estimated effect of prescribed fire on stumpage value, and secondly, we assessed wounding patterns and effects of prescribed fire on tree-quality. Loss in estimated stumpage value from prescribed fire averaged approximately 4.2% across all measured stands. Estimated loss in stumpage value varied significantly by the number of prescribed fires in the last 30 years, with increasing numbers of prescribed fires leading to higher estimated losses in stumpage value. Further, stands in Mark Twain National Forest exhibited higher estimated loss in stumpage value, exceeding 10% on average. Stands in Hoosier, Wayne, and Daniel Boone National Forest only rarely exceed 5% losses in estimated stumpage value, and averaged less than 3%. </div><div><br></div><div>Approximately 25% of trees had at least one wound associated with prescribed fire across all study sites, while approximately 5% of trees experienced a reduction in tree quality (as measured by United States Forest Service tree grade) from prescribed fire. Both the rate of wounding and rate of tree grade reduction increased with increasing numbers of prescribed fires. Stands in the western portion of the Central Hardwood Region (Hoosier and Mark Twain National Forest) exhibiting higher rates of wounding from fire compared to eastern sites (Wayne and Daniel Boone National Forest.)</div><div><br></div><div>Effects of wounding varied significantly by type of wound. Catfaces accounted for far more volume loss and reduction in tree grade than any other wound type. Alternatively, some wound types, like seams and bark slough, caused minimal tree-quality and tree-volume effects. Effects also varied by species, with higher wounding effects on sugar maple and red oak, and relatively low effects on white oak and yellow-poplar. </div><div><br></div>
4

Influence of intra- and interspecific competition on timber quality of European beech

Höwler, Kirsten 10 September 2020 (has links)
No description available.
5

Optimizing a biomass supply system: consideration of pellet quality and transportation under extreme events

Aladwan, Badr S 06 August 2021 (has links)
This dissertation studies a framework in support biomass wood pellet supply chain. The worldwide wood pellet market is growing at a phenomenal rate. However, the economic sustainment of this business depends on how well the producers manage the uncertainty associated with biomass yield and quality. In the first part of the dissertation, we propose a two-stage stochastic programming model that optimizes different critical decisions (e.g., harvesting, storage, transportation, quality inspection, and production decisions) of a biomass-to-pellet supply system under biomass yield and quality uncertainty to economically produce pellets while accounting for the different pellet standards set forward by the U.S. and European markets. The study develops a hybrid algorithm that combines Sample Average Approximation with an enhanced Progressive Hedging algorithm. We propose two parallelization schemes to efficiently speed up the convergence of the overall algorithm. We use Mississippi as a testing ground to visualize and validate the algorithms performance. Experimental results indicate that the biomass-to-pellet supply system is sensitive to the biomass quality parameters (e.g., ash and moisture contents). In the second part of the dissertation, we propose a bi-level mixed-integer linear programming model that captures important features such as the hurricane’s degree, quality of damaged timbers, price-related issues, optimizes different critical decisions (e.g., purchasing, storage, and transportation decisions) of a post-hurricane damaged timber management problem. Lack of efficient tools to manage the wood market interactions in the post-hurricane situation increases timber salvage loss drastically. The overall goal is to provide an efficient decision-making tool for planning and recovering damaged timber to maximize its monetary value and mitigate its negative ecological impacts. Due to the complexity associated with solving the proposed model, we developed two exact solution methods, namely, the enhanced Benders decomposition and the Benders-based branch-and-cut algorithms, to efficiently solve the model in a reasonable time-frame. We use 15 coastal counties in southeast Mississippi to visualize and validate the algorithms' performance. Key managerial insights are drawn on the sensitivity of a number of critical parameters, such as selling/purchasing prices offered by the landowners/mills, quality-level, and deterioration rate of the damaged timbers on their economic recovery following a natural catastrophe.

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